package interview.algorithms.again_in_interview;

import java.util.HashMap;

/**
 * @author fance
 * @date 2018/8/15 16:31
 */
class Node {
    int key;
    int value;
    Node pre;
    Node next;

    public Node(int key, int value) {
        this.key = key;
        this.value = value;
    }

}
public class LRUCache {
    HashMap<Integer, Node> map;
    int capicity, count;
    Node head, tail;
    public LRUCache(int capacity) {
        this.capicity = capacity;
        map = new HashMap<>();
        head = new Node(0, 0);
        tail = new Node(0, 0);
        head.next = tail;
        tail.pre = head;
        count = 0;
    }

    public void deleteNode(Node node) {
        node.pre.next = node.next;
        node.next.pre = node.pre;
    }

    public void addToHead(Node node) {
        node.next = head.next;
        node.next.pre = node;
        node.pre = head;
        head.next = node;
    }


    public int get(int key) {
        if (map.get(key) != null) {
            Node node = map.get(key);
            int result = node.value;
            deleteNode(node);
            addToHead(node);
            return result;
        }
        return -1;
    }

    public void set(int key, int value) {
        if (map.get(key) != null) {
            Node node = map.get(key);
            node.value = value;
            deleteNode(node);
            addToHead(node);
        } else {
            Node node = new Node(key, value);
            map.put(key, node);
            if (count < capicity) {
                count++;
                addToHead(node);
            } else {
                map.remove(tail.pre.key);
                deleteNode(tail.pre);
                addToHead(node);
            }
        }
    }
}
